Received: by 2002:ab2:3319:0:b0:1ef:7a0f:c32d with SMTP id i25csp543585lqc; Fri, 8 Mar 2024 05:25:30 -0800 (PST) X-Forwarded-Encrypted: i=3; AJvYcCV7zg/QnS53oAUFb91KqPV3MperqgVPQpw+TQD7as7UalrI9wWbVc7WuE9pqslIpi2VZIqQdS3EVIxkK74hCa6FVlAsmEXpzlCGGLcF6g== X-Google-Smtp-Source: AGHT+IGUTsG1eRAxAYRwKWWcIuIdWdDHrhQUuNOh3rsYgPIUhsLmth6UNAch1oyNXRHLK0h85d2C X-Received: by 2002:a17:902:ccc2:b0:1dd:5578:55cb with SMTP id z2-20020a170902ccc200b001dd557855cbmr5681798ple.2.1709904330451; Fri, 08 Mar 2024 05:25:30 -0800 (PST) ARC-Seal: i=2; a=rsa-sha256; t=1709904330; cv=pass; d=google.com; s=arc-20160816; b=tC/5l5hrgM+6Z6QxQRCIN7AsLcyJQM0Y/MlOeyJV6RsgtI9HsSPZcMxBGW8/47Lj12 Ve1eglkH6dpRjSfQHTkSs401VkUX7nPsoJHp7kGELIiTanLvuzMvnodybccutwgXwCQu VU89NY7oUZDT+XqNM1AXuH7nbt60ttcLqkQEDi+YX85ytODP/5s4YkYt577pX1dE36qT Evp6FdYHoOd3c7vGqCll4ZVS2AJM99xZJ1eHjVE1HtttLmxw9E1YhuTMGLcpK/5saw1G AAmdqgbWh5fU8M+JMeXzK4kiqYg+KpZPNQhhKqn6k/ZlLer1j7VyxJHyGD3DuOGE5IOA 5HIA== ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=content-transfer-encoding:in-reply-to:organization:autocrypt:from :references:cc:to:content-language:subject:user-agent:mime-version :list-unsubscribe:list-subscribe:list-id:precedence:date:message-id :dkim-signature; bh=gFlkabwZqKFxCKxsKuJlWikQ6ttLHeYy2agQBJH0FF8=; fh=iEGx2XGKbq5fcRM7idGsvLywL7mmJ56QR8nIOrGzHBk=; b=JnfDc9MMIdv/L+2jnsNcCSH5jns4ot5qEMB256JQSGDZckubsauEmjSsiQrT7x7+Wr /yaJvp/2skQn8DLNiwICPx5NSWa62z9Wnk+roedVbsYk9waer+Hjdg2VPZDApBWnNeEu TO/jkU4ytxY/4N7BBRjtgH/3xnxhBMIgskZ3XBOWmep7zmNej6avSpusEifiLnUIK+l2 ulPCLQfj2plulTudlzeYpKbuJ+vSqWmxo8rmX8KsQ5XIWFWDCqvgKzdOkSE7Uqsg/3S9 k/ST4pEX4T2lAJ8W1Ilr4UM0wlNUJPMf5Onrx/85fgf0mTGIldSZ6/zLQq3ZS9FLwO8Z 8xIA==; dara=google.com ARC-Authentication-Results: i=2; mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=jH9RxcVc; arc=pass (i=1 spf=pass spfdomain=redhat.com dkim=pass dkdomain=redhat.com dmarc=pass fromdomain=redhat.com); spf=pass (google.com: domain of linux-kernel+bounces-97074-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45e3:2400::1 as permitted sender) smtp.mailfrom="linux-kernel+bounces-97074-linux.lists.archive=gmail.com@vger.kernel.org"; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Return-Path: Received: from sv.mirrors.kernel.org (sv.mirrors.kernel.org. [2604:1380:45e3:2400::1]) by mx.google.com with ESMTPS id f8-20020a170902684800b001dbcc3280f3si2517813pln.232.2024.03.08.05.25.30 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 08 Mar 2024 05:25:30 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel+bounces-97074-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45e3:2400::1 as permitted sender) client-ip=2604:1380:45e3:2400::1; Authentication-Results: mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=jH9RxcVc; arc=pass (i=1 spf=pass spfdomain=redhat.com dkim=pass dkdomain=redhat.com dmarc=pass fromdomain=redhat.com); spf=pass (google.com: domain of linux-kernel+bounces-97074-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45e3:2400::1 as permitted sender) smtp.mailfrom="linux-kernel+bounces-97074-linux.lists.archive=gmail.com@vger.kernel.org"; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from smtp.subspace.kernel.org (wormhole.subspace.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sv.mirrors.kernel.org (Postfix) with ESMTPS id 0ADCB28524D for ; Fri, 8 Mar 2024 13:24:58 +0000 (UTC) Received: from localhost.localdomain (localhost.localdomain [127.0.0.1]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 543A41EA8F; Fri, 8 Mar 2024 13:24:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="jH9RxcVc" Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7DD8238387 for ; Fri, 8 Mar 2024 13:24:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709904261; cv=none; b=ANaDLwL4a7P1xHjo2WopNblCsZM+5pl3juEIsxG3CzDUOOw9N2qeJa8I+2fs+9j4uAKmUXb+cnf1CnR2fSrzGSXuDYsFoBV3wpZY1CVyDP882yIfmrnq1wNMTM+0pLHgX7IJ2ROv9tSDKtmwo6GW6dIWBHUKjNEv58/A//OfvQk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709904261; c=relaxed/simple; bh=ArbxbrIhMWIpMj875TH4hlv+kCQ83PAuq0Ra4SmpQxE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=A2yYJRhNcVl8+85jBHme8K6WXJ9bYJXhOL13PmwjRuzKG8B0uu1eJjni9E6dBd8lj/lHuyez1XQhCQa9rhq5ezX44EmFXTiWGoqKlHQ/THS73rT4nHetf6raK2jpySvoktMmIHHGBVYmHdSofDsWKV/qEQVdh1LiC8sWEdaT5lg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=jH9RxcVc; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1709904258; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=gFlkabwZqKFxCKxsKuJlWikQ6ttLHeYy2agQBJH0FF8=; b=jH9RxcVcS28H2J97TG/yiFYQs0V4QDEde/W9RXPiQPU5TEjVLrJlf57D5AGkpC0pLvJRrp b14oB0WjkI85dFW56SXwU+t33Oyx8NffXr3Quqqkz8nyCJF21D+PzSXByHux1tqV0YME1B W+Dfrq/pfrweaY2QZgi4WeuFAgAN9Dw= Received: from mail-wm1-f70.google.com (mail-wm1-f70.google.com [209.85.128.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-646-bUCWquOmO_2lMEm0HUfI3Q-1; Fri, 08 Mar 2024 08:24:17 -0500 X-MC-Unique: bUCWquOmO_2lMEm0HUfI3Q-1 Received: by mail-wm1-f70.google.com with SMTP id 5b1f17b1804b1-412d433bba5so4035025e9.0 for ; Fri, 08 Mar 2024 05:24:17 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1709904256; x=1710509056; h=content-transfer-encoding:in-reply-to:organization:autocrypt:from :references:cc:to:content-language:subject:user-agent:mime-version :date:message-id:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=gFlkabwZqKFxCKxsKuJlWikQ6ttLHeYy2agQBJH0FF8=; b=XfqtAe7eK6QqGXaFmSCyZqPJUc9fI7buzmJokRII0gHcZ4OpQ9V7F4xIlqOb80urE9 cX744d55zQbc4YRRSSzG/OhbGWNtibWLHvNXkmvQlGQCEpasI1IJj0gOubLF/nHiYIbP IJcC5bsxYoVCu6ts+QQ/JsjjdZGtmMage/R/j+DvzZ01Z/RNP0N1bWps9yLV8I4Y/DEU nZXa/dj7fw9Atj9mh8mbSH9ejgeLVsb5a9K4bsAK4MhHkFWVMnPQ3H6wOvCbLx9Vf6UL nTsSj4nOK8qOsGdJ5b8LWZjW7B4Pu9W8z7MvUe+JlJlxVva7eRL5L9M21M8qqAVZCy+M QGtg== X-Forwarded-Encrypted: i=1; AJvYcCVsQfzooblV67ebVHK+FgGCAPztJcx5Q8T6G1N8HZ1Uhv6VfCOrzg64EnsOh3h/E05OAsyR0B6xpRPfqifLanvh4YYAZRg1wIHncHn2 X-Gm-Message-State: AOJu0YwGICVaWn/2RT3Tl5E3nyR4r7Lt24PZcNEt20ICmcVgr8RCl1ha cVdDGCFo7fyN/rEprcApcfFbdU9owH1PRsWsHvG5YH1j6mj6MNiMyHnW/iUJYaf7Z7i+NogK8pq eKzDn9K2RWOnwNwii4HJsTC/Nq45fFR+r4aSV2qZaEo8417qqfvcujgAd2ihWdQ== X-Received: by 2002:a05:600c:4f4d:b0:412:eb6e:1fdb with SMTP id m13-20020a05600c4f4d00b00412eb6e1fdbmr7091015wmq.40.1709904256037; Fri, 08 Mar 2024 05:24:16 -0800 (PST) X-Received: by 2002:a05:600c:4f4d:b0:412:eb6e:1fdb with SMTP id m13-20020a05600c4f4d00b00412eb6e1fdbmr7090998wmq.40.1709904255604; Fri, 08 Mar 2024 05:24:15 -0800 (PST) Received: from ?IPV6:2003:cb:c707:3500:5cd0:78d9:ca49:21f3? (p200300cbc70735005cd078d9ca4921f3.dip0.t-ipconnect.de. [2003:cb:c707:3500:5cd0:78d9:ca49:21f3]) by smtp.gmail.com with ESMTPSA id m8-20020a05600c4f4800b00413177c3f1dsm2265842wmq.18.2024.03.08.05.24.13 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 08 Mar 2024 05:24:14 -0800 (PST) Message-ID: <8e994734-1d3a-4c51-9c0b-4e2ce945f198@redhat.com> Date: Fri, 8 Mar 2024 14:24:13 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] mm: prohibit the last subpage from reusing the entire large folio Content-Language: en-US To: Ryan Roberts , Barry Song <21cnbao@gmail.com>, akpm@linux-foundation.org, linux-mm@kvack.org Cc: minchan@kernel.org, fengwei.yin@intel.com, linux-kernel@vger.kernel.org, mhocko@suse.com, peterx@redhat.com, shy828301@gmail.com, songmuchun@bytedance.com, wangkefeng.wang@huawei.com, xiehuan09@gmail.com, zokeefe@google.com, chrisl@kernel.org, yuzhao@google.com, Barry Song , Lance Yang References: <20240308092721.144735-1-21cnbao@gmail.com> <519fd6a7-072e-43a2-a9a8-2467ee783524@redhat.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit >>> This patch migrates the last subpage to a small folio and immediately >>> returns the large folio to the system. It benefits both memory availability >>> and anti-fragmentation. >> >> It might be controversial optimization, and as Ryan said, there, are likely >> other cases where we'd want to migrate off-of a thp if possible earlier. > > Personally, I think there might also be cases where you want to copy/reuse the > entire large folio. If you're application is using 16K THPs perhaps it's a > bigger win to just treat it like a base page? I expect the cost/benefit will > change as the THP size increases? Yes, I think for small folios (i.e., 16KiB) it will be rather easy to make a decision. The larger the folio, the larger the page fault latency due to scanning, copying, modifying, which can easily turn undesirable. At least when it comes to page reuse, I have some simple backup plans for small folios if I won't be able to make progress with my other approach. For larger folios, it won't really work/be desirable, though. -- Cheers, David / dhildenb